Port to Minecraft 26.1.2

[mmkk20158]

Summary

Ports SchematicPreview to Minecraft 26.1.2 (Fabric Loader 0.19.2, Fabric API 0.150.0+26.1.2, MaLiLib 0.28.6, Litematica 0.27.6).

This work was generated entirely with AI assistance (Cursor) and has been tested in-game on 26.1.2 with a real modpack. Preview rendering, textures, schematic browser thumbnails, side-panel interaction, and stability were verified working.

Changes

• Update build toolchain for 26.1 unobfuscated mappings (Fabric Loom 1.16.x, Gradle 9.4, Java 25)
• Port GUI widgets to MaLiLib GuiContext / 26.1 render-state APIs
• Port schematic preview rendering to 26.1 chunk/GPU pipeline (BlockModelRendererSchematic, offscreen TextureTarget, manual render passes)
• Fix preview drawing to offscreen framebuffer instead of main render target
• Fix ConcurrentModificationException from parallel chunk mesh builds (per-chunk renderer instances)
• Fix preview flicker (avoid unnecessary full clears/redraws every frame)
• Fix incorrect block textures (bind block atlas on Sampler0)
• Update WorldSchematicWrapper for 26.1 BlockAndTintGetter API

Version

0.0.20+26.1.2

Test plan

• Mod loads on Minecraft 26.1.2 with Litematica + MaLiLib
• Schematic browser side preview renders correctly
• List thumbnails render without flashing
• Block textures appear correct (block entities e.g. chests also look correct)
• Rotate / zoom / freecam / fullscreen preview work
• No crash from parallel chunk mesh building when browsing schematics

Happy to adjust anything to match upstream conventions or split this into smaller PRs if preferred.